Sean Williams played a key role in bringing Courtney Lee to Boston.When the Celtics inked Sean Williams in the final week of the 2011-12 regular season, it was a move that barely got your attention with the playoffs nearing. Boston essentially had an open roster spot with Jermaine O'Neal having undergone season-ending wrist surgery and the team signed Williams with the goal of giving him a chance to compete for a roster spot this summer.

Call it a $49,966 investment in the 2012-13 season.

Without Williams' nonguaranteed contract at their disposal this summer, Courtney Lee might not have ended up in Boston. The Celtics were able to bundle Williams with E'Twaun Moore, JaJuan Johnson, Sasha Pavlovic, a trio of second-round picks, and some cash as part of a three-team sign-and-trade that was finalized Friday and allowed Boston to ink Lee to a four-year deal.

Boston gave up non-essential, end-of-the-bench depth -- including a player like Williams that was a longshot to make the roster -- to bring in a player that will compete for a starting job. Williams (and Moore) is expected to be waived by cap-conscious Houston and will be left searching for his next NBA opportunity, but he'll have played a major role in helping how the Celtics' 2012-13 roster was constructed.

With that in mind, an updated glance at where Boston stands after Friday's deal:

A handful of thoughts as the Celtics look to complete their offseason roster construction:

* Boston is practically on the $70.4 million luxury tax threshold (teams have to stay within a $4 million apron of that line in order to use the full $5 million midlevel exception). The Celtics are hard-capped at this point and must figure out economical ways to fill out their roster. While second-round pick Joseph's spot seems pretty secure after a solid summer, it wouldn't be a surprise to see Boston carry a 14-man roster at the start of the year and let summer standouts like Jamar Smith (nonguaranteed deal with a camp invite) and Dionte Christmas (who could camp with the team as well, if he can resist the immediate security of an overseas deal) compete for a low-cost spot.

* As for remaining needs, Boston could seemingly benefit from adding one more legitimate big man. But it almost certainly won't be Stiemsma. While the Celtics were hoping they might be able to bring him back at the $1.05 million qualifying offer extended before the start of free agency, the restricted free agent got an outside offer Friday and it's believed to be more than Boston can match given cap constraints. Boston is set to lose a young player it really likes, but added center depth already by bringing back Wilcox on a minimum deal.

* The Celtics still have the biannual exception ($1.975 million) available, but that doesn't mean they have to use it (or at least all of it). Given how close they appear to be (with our estimated numbers) to their cap, it might benefit Boston to stash the biannual and have it at their disposal to absorb (and entice) more than a minimum contract at the waiver deadline later in the season (but remember, they still have to leave themselves the necessary room to use it at that point and stay under $74.3 million overall). Boston and other contenders have been left playing tug-of-war for waived players in recent seasons, but having more than the minimum to offer could help Boston snag an impact body down the road.

* Boston's other glaring need: A backup point guard. Terry can tackle some ball-handling duties behind Rondo, while Smith or Christmas could make a bid for a roster spot if they proved capable of assisting with those duties (the way the team hoped Moore could as a combo guard before being dealt away). The other option here: Dooling, who could either be re-signed utilizing his Bird rights, or Boston could renounce those and ink him to a minimum deal (if he were willing to accept). That would give the Celtics additional veteran depth at both guard spots and a solid locker room presence.

* The Celtics have seemed somewhat lukewarm on Pietrus this summer and clearly targeted the likes of Lee as priorities over him. That said, they only had the biannual to offer Pietrus, who has patiently waited to see how the market plays out. Pietrus, even coming off a second knee surgery this summer, might find himself more in demand now from other contenders looking for wing depth and those teams might be able to offer a bigger role than what Boston has remaining after adding Terry and Lee.